package com.zh.core;

/**
 * Created by zhaohui on 2019/11/7
 */
public class MatrixMinPathSum {

    public static int minPathSum1(int[][] m) {
        if (m == null || m[0] == null || m.length == 0 || m[0].length == 0) {
            return 0;
        }
        int row = m.length;
        int col = m[0].length;
        int[][] dp = new int[row][col];
        dp[0][0] = m[0][0];
        for (int i = 1; i < row; i++) {
            dp[i][0] = dp[i-1][0] + m[i][0];
        }
        for (int j = 1; j < col; j++) {
            dp[0][j] = dp[0][j-1] + m[0][j];
        }
        for (int i = 1; i < row; i++) {
            for (int j = 1; j < col; j++) {
                dp[i][j] = Math.min(dp[i-1][j], dp[i][j-1]) + m[i][j];
            }
        }
        return dp[row-1][col-1];
    }

    public static int minPathSum2(int[][] m) {
        int more = Math.max(m.length, m[0].length);
        int less = Math.min(m.length, m[0].length);
        // 行数是否比列数更多，是，则逐行更新，否，则逐列更新
        boolean rowmore = more == m.length;
        int[] arr = new int[less];
        arr[0] = m[0][0];
        for (int i = 1; i < less; i++) {
            arr[i] = arr[i-1] + (rowmore ? m[0][i] : m[i][0]);
        }
        for (int i = 1; i < more; i++) {
            arr[0] = arr[0] + (rowmore ? m[i][0] : m[0][i]);
            for (int j = 1; j < less; j++) {
                arr[j] = Math.min(arr[j-1], arr[j]) + (rowmore ? m[i][j] : m[j][i]);
            }
        }
        return arr[less-1];
    }

    public static void main(String[] args) {
        int[][] m = {
                {1, 3, 5, 9, 4},
                {8, 1, 3, 4, 2},
                {5, 0, 6, 1, 0},
                {8, 8, 4, 0, 3}
        };
        System.out.println(minPathSum1(m));
        System.out.println(minPathSum2(m));
    }

}
